The world is at risk of entering "greenhouse" conditions where average global temperatures will be 4 to 5 degrees Celsius even if emission reduction targets in a global climate agreement are met, scientists said in a study published Monday.
The report comes amid a heat wave that has pushed temperatures above 40 ° C (104 Fahrenheit) in Europe this summer, leading to droughts and wildfires, including fires in Greece in July that killed 91 people.
About 200 countries agreed in 2015 to limit temperature rise to "well below" 2C (3.6F) above pre-industrial levels, a threshold believed to be a tipping point for the climate.
However, it is not clear if the global climate can be safely 'parked' about 2ºC above pre-industrial levels or if this could trigger other processes that cause further warming even if the world stops emitting greenhouse gases. , according to research.
Currently, global average temperatures are a little more than 1ºC above the pre-industrial period and increase to 0.17ºC every decade.
Scientists from the Stockholm Resilience Center, the University of Copenhagen, the Australian National University and the Potsdam Institute for Climate Impact Research said it is likely that if a critical threshold is crossed, several tipping points will lead to abrupt change.
Such processes include permafrost thawing; the loss of methane hydrates from the ocean floor; weaker terrestrial and oceanic carbon sinks; the loss of Arctic summer sea ice and the reduction of Antarctic sea ice and polar ice sheets.
“These turning items can potentially act like a row of dominoes. Once it is pushed, it pushes the Earth towards another, ”said Johan Rockström, co-author of the report published in the Proceedings of the National Academy of Sciences and executive director of the Stockholm Resilience Center.
“It can be very difficult or impossible to prevent the entire row of dominoes from falling apart. Places on Earth will become uninhabitable if 'Hothouse Earth' becomes a reality, ”he said.
Maximizing the chances of avoiding this "greenhouse" state requires more than simply reducing greenhouse gas emissions, according to the report.
For example, improved management of forests, agriculture and soil; conservation of biodiversity and technologies that remove carbon dioxide from the atmosphere and store it underground are necessary.
Commenting on the research, some experts said that runaway warming remains uncertain but not implausible.
"In the context of the summer of 2018, this is definitely not a crying wolf case, which raises a false alarm: the wolves are now in sight," said Phil Williamson, a climate researcher at the University of East Anglia.
Original article (in English)